The invention relates to an air intake device for internal combustion engines
An air intake device is disclosed in DE 40 03 492. It provides for a collector which is rotatable about its axis. A part that is continuously variable in length branches out to each cylinder of the internal combustion engine. This part is an intake duct made of a synthetic resin tube of flexible length and is reinforced by spiral springs.
A disadvantage of this air intake device is that the tube disposed outside of the collector becomes dirty, and moreover there is a danger that the tube may break or become leaky due to mechanical influences.
Another disadvantage is that atmospheric pressure bears against an externally situated tube. With increasing engine speed and consequently increasing vacuum in the air intake, the tube thus is increasingly exposed to mechanical stress. Unless reinforced by a spiral spring the tube walls must be so stiff that, in an intake tube of continuously variable length, the possible variation in length is too greatly limited, and with it the maximum possible range of adjustment.
Precisely in the case of air intake systems for internal combustion engines it is necessary to make the possible change of length as great as possible in order to optimally adapt the air intake line to the corresponding engine speed. In the state of the art the adaptation can only be made by a rotation of approximately 270xc2x0. EP 0 747 584 furthermore discloses an air intake system for an internal combustion engine in which a pivotable intake tube portion is provided. By pivoting this intake tube portion, two predefined intake tube lengths can be established. A variable adaptation of the intake tube length is not possible.
DE 38 25 000 describes an air intake duct of internal combustion engines with a continuously variable effective length, wherein an intake channel is provided in which a slide is mounted. A channel is opened or closed and the channel length adjusted depending on the position of the slide. A disadvantage of this system is that the structure involves large friction losses and the arrangement of the slide in the air intake duct of an internal combustion engine can be achieved industrially only at a disproportionately great cost.
It is therefore the object of the invention to provide an air intake device which avoids the described disadvantages, can be manufactured economically and operates reliably. This object is achieved by the invention as described and claimed hereinafter.
The substantial advantages of the invention lie in the fact that a flexible tube is also used for the intake ducts, but it is arranged to be protected within the collector.
According to one embodiment of the invention, the length and the diameter of the flexible tube can be adapted in a simple manner to the particular internal combustion engine. For example, in the case of an internal combustion engine of lower displacement volume, smaller tube diameters are needed, and in an internal combustion engine with a larger displacement volume, larger intake diameters and possibly also greater tube lengths are necessary. The air intake device can therefore be optimally adapted to the motor in question.
According to an additional embodiment of the invention the length of the flexible tube can also be varied as steplessly as desired. For this purpose the mouth of the flexible tube lies, for example, on a supporting body that is mounted for rotation. The tube also can be in contact with this supporting body. Of course, it is also possible to lengthen or shorten the flexible tube rectilinearly. In this case the supporting body would perform a longitudinal movement. The flexible tube is variable in lenght both rectilinearly and arcuately or circularly.
These and additional features of preferred embodiments of the invention will be found not only in the claims but also in the description and the drawings, and the individual features can be realized each by itself or together in the form of subcombinations in the embodiment of the invention and in other fields, and can constitute advantageous as well as independently patentable embodiments, for which protection is hereby claimed.